[Thai Details]

Additional validation rules for Thai:

References for contextual rules

RFC 5891: "Internationalized Domain Names in Applications (IDNA): Protocol" 
   (proposed standard), http://tools.ietf.org/html/rfc5891

".SCB IDN Registration Policy" by Thai Name Server Co.,Ltd,
   http://web.thains.co.th/docs/scb/SCB_IDN_Policy.pdf

Code point                  Description of rule/Reference

U+002D                      Label must neither start nor end with U+002D. Label 
   HYPHEN-MINUS             must not have U+002D in both third and fourth
                            position. RFC 5891 (sec 4.2.3.1)


U+0E31, 0E34..0E3A,         Not in initial position. RFC 5891 (4.2.3.2).
0E46..0E4E
   Marks and Modifier
   Letter

0E40..0E44                  Must be directly followed by a code point of 
   Leading Vowels          0E01..0E2E.

U+0E31, U+0E34..U+0E37,     Must be directly preceded by a code point of 
U+0E47, U+0E4C..U+0E4D      0E01..0E2E.
   Upper Vowel Symbol
   and Upper Diacritics

0E48..0E4B                  Must be directly preceded by a code point of 
   Tone Marks               0E01..0E2E or U+0E31, U+0E34..U+0E37, U+0E47, 
                            U+0E4C..U+0E4E. Must not be followed by a
                            code point of U+0E31, U+0E34..U+0E37, U+0E47, 
                            U+0E4C..U+0E4E.

U+0E30, U+0E32, U+0E45      Must be directly preceded by a code point of 
   Following Vowels         0E01..0E2E or a code point of U+0E31, 
                            U+0E34..U+0E37, U+0E47, U+0E4C..U+0E4E or a
                            code point of 0E48..0E4B.

U+0E38..U+0E3A              Must be directly preceded by a code point of 
   Lower Vowel Symbols      0E01..0E2E or a code point of U+0E31, 
                            U+0E34..U+0E37, U+0E47, U+0E4C..U+0E4E or a
                            code point of 0E48..0E4B.